If your my.cnf file is not configured optimally, MySQL may be loading up the RAM it is allowed to use (perhaps showing a CPU spike), but then starting swapping out to disk (temp files) when it hits it's RAM allocation. Since this is MySQL hitting a RAM allocation limit and not the system running out of RAM, you won't see the OS indicating page outs, which would indicate not enough RAM.
Usually, the two parameters that help the most in the my.cnf file is the key_buffer and sort_buffer_size. If your complaints are coming from Forum and Picture Gallery, your bottleneck may be in disk I/O. I always try to put the OS on it's own disk like you, but if I only have two disks, I'll mirror the two disks to increase read speeds. Although it's then double important that you system has enough RAM since your writes will be slower (think slow memory paging). Of course, if you want to live dangerously, which you are just about doing anyway with no mirroring, you can stripe your disks and get better read and write speeds.
But first play with you my.cnf parameters to see if things speed up. Also, read the manual:
http://dev.mysql.com/doc/mysql/en/Optimising_the_Server.html
On Jun 21, 2004, at 12:10 AM, Eric Wagar wrote:
I have a Sun Netra T1 with 512MB of ram and 2 x 9G drives. (One is exclusively the MySQL 3.23.56 files, and the other is OS, Apache, etc.) I am also using the default medium (I think) my.cnf.
Currently, the complaints are coming from a php Forum and a php picture Gallery. From the OS side, I don't see any problems, along with the Apache side. So, I am leaning towards an improper MySQL configuration.
Where do I go to get more information on where to start looking for performance issues for the DB?
-- Brent Baisley Systems Architect Landover Associates, Inc. Search & Advisory Services for Advanced Technology Environments p: 212.759.6400/800.759.0577
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